Recent studies suggest that Pseudomonas aeruginosa is one of the most significant respiratory pathogen in patients with cystic fibrosis and is a common cause of nosocomial lung infection in hospitalized and immunocompromised patients. In accordance with the mission of the NHLBI to improve the care of patients with lung disease, this proposal will examine the mechanisms regulating host-pathogen interactions in P. aeruginosa pulmonary infection and may identify new strategies for this difficult clinical problem. The first point of contact for many respiratory pathogens including bacteria is the airway epithelium. To defend against bacterial colonization and infection in the airways, lung epithelial cells direct and regulate the appropriate immune response through production of antimicrobial peptides, lipid mediators, pro-inflammatory cytokines, and hence interaction with hematopoietic cells. These innate defense mechanisms are in part controlled by effector mediators such as MMPs. Early studies indicate that one MMP in particular, stromelysin-2 (MMP-10) serves to modulate the inflammatory response by the epithelial cells. However, the exact mechanism is unclear. Thus, the overall objective of this proposal is to study the mechanisms of stromelysin-2 regulated inflammation using a systems-based proteomics approach to complement the studies in animal models of P. aeruginosa-induced lung inflammation. As inflammation processes are complex and involve multiple cells and pathways, we will use mice deficient instromelysin-2 to study its relative contribution to inflammation, particularly in macrophage function. In addition, we will perform a proteomic analysis of epithelial cultures derived from these and wildtype mice to identify proteins that are substrates of stromelysin-2 and determine the role of these proteins in macrophage chemotaxis and activation and P. aeruginosa - induced lung inflammation. The studies in this proposal will attempt to define key proteins and functional mechanisms underlying acute lung inflammation. Determining and understanding these mediators are important when translation into therapeutic use against diseases such as acute lung injury and pneumonia is needed.